A social network, in general, is a social structure made up of entities, such as individuals or organizations, that are connected by one or more types of interdependency or relationships, such as friendship, kinship, common interest, financial exchange, dislike, or relationships of beliefs, knowledge, or prestige. In more recent years, social networks have taken advantage of the Internet. There are social networks existing on the Internet in form of social networking systems. Such social networking systems enable their users, who are commonly referred to as website users, to perform various social activities. For example, the social networking system operated by Facebook, Inc. at facebook.com enables its users to communicate with their friends via emails, instant messages, or blog postings, organize social events, share photos, receive news of their friends or interesting events, use social applications, etc.